Facebook has a lot to live up to as the poster child for the social-media movement enters its second decade in business.

“Facebook obviously has a huge audience and provides a real service as a way of keeping track of a loose network of friends, but it will struggle to expand its brief beyond what it’s currently doing,” said Paul Carroll, co-author of “The New Killer Apps: How Large Companies Can Out-Innovate Start-Ups.”

Already boasting some 1.2 billion “friends,” CEO Mark Zuckerberg’s brainchild must prove that it can continue to grow despite the possibility that it has already begun to saturate its most fertile marketplaces while facing stiff competition in key foreign centers.

Where will Facebook’s next generation of users come from, then?

“The Western markets are showing signs of maturing, and there is only so much you can do in Asia,” noted Tony Wible, an analyst for Janney Capital Markets.

Facebook also has the challenge of continually monetizing that gargantuan user base to appeal to advertisers. The problem is, Facebook is hardly the only game in town. The social-media space is crowded, with entities like Twitter and Linked­In — and Facebook will certainty continue to encounter additional rivals down the road.

It’s ironic that a company that Zuckerberg created on a college campus has to contend with whispers that its appeal is slipping among high-school and college students.

“Facebook’s biggest challenge is to keep its users engaged,” Wible said. “The company has set a high bar, and it has to think up new ways to hook people.”

Facebook may be standing on the wrong side of the generation gap.

In fact, plenty of teens and tweens are turned off by “Mommy-book”: They just don’t want to appear on a social-media site that their oh-so-uncool parents love and use liberally.

“Facebook is losing its cool factor,” Carroll pointed out. “This is already showing up in the declining interest among teens.”

Further, Zuckerberg, who will turn 30 on May 14 and reportedly has a net worth of roughly $24 billion, has the burden of fighting human complacency while fending off a slew of formidable competitors.

But it would be worse than foolish to write off Facebook’s ability to meet the challenge.

“This is a company,” said Wible, “that still has a lot of dry powder that it hasn’t had to use yet.”